Description Solid gray above and below with short tail, the largest shrew in North America.

Dimensions 95-139mm, 17-32mm, 11-30g

Warning The shrews of the genus Blarina are unique among mammals in producing poison in their salivary glands. The saliva is not dangerous to humans, but a bite may swell and be painful for several days.

Breeding Mating occurs from March through September, though most births occur early or late in that period. Gestation lasts 21-22 days, and after birth the 4-7 young nurse for up to 25 days. Two litters per season are typical. The young, born hairless and blind, weigh less than a gram and may become sexually mature in as soon as 2-3 months.

Discussion Its ability to consume almost anything it can catch allows the Northern Short-tailed Shrew to survive the cold winters of temperate regions. Other shrews spend more time above ground than does the Northern Short-tailed Shrew, which prefers to tunnel along below ground, through the leaf litter, or at the snow/ground interface. Bouts of frenzied activity, lasting approximately five minutes, are followed by longer periods of resting, with the total active time amounting to only 16% of a 24-hour day. The shrew constructs a nest up to 20 centimeters (8 inches) in diameter underground or underneath a log, and lines it with leaves or the fur of the Meadow Vole (Microtus pennsylvanicus).This nest is kept clean, with wastes deposited outside the nest in a latrine area. Other parts of the burrow system are used for food storage.